As is known, an electro-optic element having a plurality of individually addressable electrodes may be employed as a multigate light valve in, say, an electro-optic line printer. See a copending and commonly assigned U.S. patent application of R. A. Sprague et al., which was filed June 21, 1979 under Ser. No. 040,607 on a "TIR Electro-Optic Modulator with Individually Addressable Electrodes" (now U.S. Pat. No. 4,281,904). Also see, "Light Gates Give Data Recorder Improved Hardcopy Resolution," Electronic Design, July 19, 1979, pp. 31-32; "Polarizing Filters Plot Analog Waveforms," Machine Design, Vol. 51, No. 17, July 26, 1979, p. 62; and "Data Recorder Eliminates Problem of Linearity," Design News, Feb. 4, 1980, pp. 56-57.
Substantial progress has been made in developing such light valves and in applying them to electro-optic line printing. For example, a copending and commonly assigned U.S. patent application of R. A. Sprague, which was filed Sept. 17, 1980 under Ser. No. 187,911 on an "Electro-Optic Line Printer," now U.S. Pat. No. 4,389,659 shows that an image represented by a serial input data stream may be printed on a standard photosensitive recording medium through the use of a multistage light valve that is illuminated by a more or less conventional light source. That disclosure is of interest primarily because it teaches input data sample and hold techniques for minimizing the output power required of the light source. Another copending and commonly assigned U.S. patent application of W. D. Turner, which was filed Sept. 17, 1980 under Ser. No. 187,936 on "Proximity Coupled Electro-Optic Devices," reveals that the electrodes and the electro-optic element of a multigate light valve may be physically distinct components which are pressed or otherwise firmly held together to achieve "proximity coupling." Still another copending and commonly assigned U.S. patent application of R. A. Sprague et al. which was filed Sept. 17, 1980 under Ser. No. 188,171 on "Integrated Electronic for Proximity Coupled Electro-Optic Devices," (now U.S. Pat. No. 4,367,925) shows that it is relatively easy to make the necessary electrical connections to the many electrodes of a typical proximity coupled multigate light valve if the electrodes are formed by suitably patterning a metallization layer of, say, a VLSI silicon electrode driver circuit. Furthermore, yet another copending and commonly assigned U.S. patent application of W. D. Turner et al., which was filed Sept. 17, 1980 under Ser. No. 187,916 on "Differential Encoding for Fringe Field Responsive Electro-Optic Line Printers," teaches that the number of electrodes required of a multigate light valve to enable an electro-optic line printer to achieve a given resolution is reduced by a factor of two if the input data is differentially encoded.
Prior fringe field reponsive multigate light valves, such as the TIR light valves described in several of the above-identified disclosures, have been characteristically configured so that all of the electrodes are effectively within a single plane. It has been recognized that there are potential advantages to reducing the spacing between the electrodes (i.e., the "interelectrode gap spacing"); not only to accommodate increased electrode densities, but also to obtain improved electro-optic efficiency. As will be appreciated, the resolution that can be achieved per unit width of such a light valve is directly dependent on the electrode density. However, another significant reason for being interested in reduced interelectrode gap spacings is the somewhat surprising finding that the strength of the electric fringe fields coupled into the electro-optic element of such a light valve seem to increase as the ratio of the interelectrode gap width to the center to center spacing of the individual electrodes decreases.
Unfortunately, a finite interelectrode gap spacing is required when the electrodes are all confined to a single plane. Indeed, the process used to fabricate the electrodes is likely to impose a lower limit on the interelectrode gap spacing that can be realized. For example, if the electrodes are formed photolithographically, the minimum obtainable interelectrode gap spacing is determined by the maximum available resolution of the photolithographic process.